UPSC Prelims 2013 · GS Paper I
Question 93: Science and Technology
Which of the following statements is/are correct?
- 1.Viruses lack enzymes necessary for the generation of energy.
- 2.Viruses can be cultured in any synthetic medium.
- 3.Viruses are transmitted from one organism to another by biological vectors only.
Select the correct answer using the codes given below.
AnswerUPSC’s answer is (a).
Viruses are not cells and have no metabolic machinery of their own; they lack the enzymes needed to generate energy and make proteins, so they depend on the host cell. For the same reason they cannot be cultured in synthetic media, only in living cells, tissue cultures or embryonated eggs. They spread by many routes, such as droplets, contact, contaminated food and water, as well as by vectors, so not by biological vectors only. Only statement 1 is correct.
- 1. Viruses lack enzymes for energy generation.
- 2. Viruses need living host cells, not synthetic media.
- 3. They spread through air, contact, food and water as well as vectors.
How you could have got this
- If you were sure statement 3 is not correct, (b), (c) and (d) go: each of them includes 3.
What you needed to know: They spread through air, contact, food and water as well as vectors.
The red flag in statement 3 is “only”. In UPSC’s papers, statements with “only” were true 27% of the time (82 statements). A hint, not a rule.
Only (a) is left. You didn’t need statements 1 or 2.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) Correct. Only statement 1 is true.
- (b) Wrong. Viruses cannot be grown in synthetic media, and they have many routes of spread.
- (c) Wrong. Viruses spread in many ways, not by biological vectors only.
- (d) Wrong. Statements 2 and 3 are false.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2013, General Studies Paper I, Series A. The paper on upsc.gov.in.